In a typical multimedia conferencing facility, a conference server includes a conference bridge having a number of ports to which participants can connect (e.g. by dialing up over an ISDN line or over the Internet).
Typically each participant will have a multimedia terminal which might include a video camera, display unit (such as a computer monitor), microphone and loudspeaker (e.g. as part of a telephone set connected to the terminal), and data transmission equipment (such as a computer to allow for applications such as file transfers, database access, electronic whiteboards), all connected to the ISDN line or the Internet.
Each participant connects to a port of the bridge and the conference server establishes the communications protocols to enable exchange of signals. Once the conference is underway, the conference server receives the multimedia stream from each participant, separates the channels from each stream, mixes the signals as appropriate and generates a return media stream to each participant.
Each participant will typically be sending a number of channels or streams of information to the conference server, such as video, audio, data, and control signals. The conference server receives the various video signals and may select the signal of one party to be sent as an outgoing signal to all of the parties, or it may perform a more sophisticated mixing operation on the signals, such as selecting a “current” signal, and combining this with the signals from the three most recent “current” signals, to generate a composite signal including the presence of the four most recent speakers, including the current speaker. Alternatively, and depending on the number of participants and available processing power, a composite signal of all participants may be generated by the server and broadcast to each port.
The incoming audio streams may be similarly decoded, mixed and re-encoded as a composite signal, or a single audio stream may be broadcast to all parties (i.e. the audio signal corresponding to the “current” video image).
In addition to decoding, mixing, and generating audio and video signals, the conference server will handle data streams, such as file exchanges, and whiteboard messages.
The conference server, in conjunction with a call server, also manages the connections of the participants to the conference, which involves establishing communications protocols, maintaining a listing of the participants' addresses and aliases (the address will typically be the Internet address, while the alias may be an email address or a name which is more user friendly. Communication at this level is achieved by a relatively low bandwidth control channel or stream.
Not all of the media streams need be present: thus it is possible to have audio and video channels only to and from each port, without a separate data channel, or the video channel may be omitted and an audio/data conference may be held. If some or all of the users are not computer-based, they may have telephones with display screens capable of displaying a reasonable amount of information, at least in text form. In such systems, the server can be arranged to provide each user with a listing of the users to the conference, over the control channels to the user, with that listing being displayed on the display screens of the users.
The server may be combined with and incorporated in a switching system such as a telephone exchange or its multimedia equivalent or extension. Alternatively, the server may be coupled to but distinct from such a standard switching system, with the switching system recognising the control signals indicating a conference call request and coupling the caller to the server for subsequent processing of the call.
Among the objects of the invention are the provision of a conference call server with enhanced capabilities, and the provision of an improved method of conferencing.